The present invention pertains to a device for actuating a slide in a lifting or clamping device, especially for folding sheet metals in automobile manufacture, wherein a slide that is guided in a base and can be driven with a folding bed lying on it presses the sheet metals to be folded against stationary folding tools.
In U.S. Pat. No. 5,150,508 discloses a prior-art device of the type described in the introduction. The folding stroke and the needed folding force are brought about by a central hydraulic cylinder located under the slide. In DE 197 47 291 another embodiment of this type has a compressed air cushion located under the slide. The slide moves the folding bed and the workpiece (body sheet metal) located therein against the stationary prefolding and finishing folding tools, which are fastened to displaceable and pivotable means.
The object of the present invention is to do away with hydraulic or pneumatic systems for generating and transmitting the necessary force.
This object is accomplished by the slide with its side facing the workpiece being supported on at least one wedge surface, which can be adjusted by means of an electric motor. In particular, a wedge having a wedge surface can be guided at the base, which wedge can be adjusted by means of an electric motor. The wedge is preferably adjustable essentially at right angles to the working direction of the slide.
In a preferred embodiment of the present invention, a spindle nut is arranged at the wedge for a spindle that is guided therein and can be driven by means of an electric motor. The wedge is adjusted during the rotation of the spindle and the slide is thus raised or lowered. In a space-saving arrangement, the spindle nut is accommodated in a recess of the wedge. The recess is preferably a stepped hole, whose section with the greater diameter accommodates the spindle nut and in whose section with the small diameter the end of the spindle can move. The spindle nut preferably has a recirculating ball thread.
The spindle can be connected to an electric motor via a coupling. The electric motor is preferably controlled by a frequency converter. A transmission may be advantageously intercalated between the electric motor and the coupling. The spindle may be guided in an self-aligning roller thrust bearing on the motor side.
Furthermore, it has proved to be favorable for two wedges with wedge surfaces to be arranged in opposite directions being able to be adjusted simultaneously in opposite directions via a threaded drive with left-hand and right-hand threads and to act on a wedge connected to the slide with associated wedge surfaces. During the rotation of the spindle, which is driven by an electric motor, the two wedges are pushed together or moved apart by the left-hand and right-hand threads of the spindle via the spindle nuts. The consequence of this is that the wedge connected to the slide is moved correspondingly to and fro.
The device, which is preferably called an electromechanical lifting unit, can be used, among other things, in the fields of clamping technique, folding and hemming technique and also in special areas of materials handling technology.